Inside the ex-Yankees’ cheating past.

Jennifer Lopez should have paid more attention to Alex Rodriguez’s romantic history. Just three months after she began dating the ex-Yankees slugger (who’s infamous for cheating on his girlfriends), history has come back to haunt her in the form of a secret A-Rod lover who’s come forward to claim he’s been asking her to send him raunchy videos and even trying to meet up with her — all while he’s been seeing J.Lo!

“I think [Jennifer’s] going to be shocked,” says Lauren Hunter, 34, a stunning mother of three who’s been seeing Alex on and off behind the scenes for six years. “And I don’t believe he’s sexually attracted to Jennifer. I feel like their relationship is more like a contract.”

IF JENNIFER ONLY KNEW!

In the series of recent text messages and videos that Lauren has provided (see sidebar), Alex, 41, constantly prods the one-time fitness instructor to FaceTime, and send sexy videos, and even tries to arrange a meeting in Kansas City behind J.Lo’s back.

In fact, Lauren claims that only a week after he first went public with J.Lo, 47, during a trip to the Bahamas in March, Alex “started FaceTiming me three or four times a day.” While their conversations continued, Lauren says she eventually felt it was “a ploy to be nice” by A-Rod in order to get her to agree to meet up with him in May near her home in the Midwest for a tryst.

The meeting never happened due to scheduling issues, says Lauren, and feeling betrayed when she didn’t hear from Alex for a number of weeks afterward, she’s decided to spill the beans about their relationship.

HIS HEARTBREAK HABIT

If it’s any comfort, J.Lo has lots of company when it comes to Alex’s two-timing. In 2008, he was divorced by his wife of six years, Cynthia Rodriguez, who cited his alleged extramarital affairs. And, in fact, when Lauren first met A-Rod in 2011, he was in a relationship with another actress — Cameron Diaz. “I met him at… Equinox [fitness club] in West Hollywood. I slept with him and then he went to the MTV Awards with her,” she relates. “I can’t tell you how many times we slept together while they were together.”

Lauren describes Alex as “rough” in bed but “loving and sweet” out of the sack, and claims that the very first time they were intimate, he told her, “I wanna marry you, I want you to have my kids.” One of the many reasons that never happened, says Lauren, is because Alex “cares more about image” — which means dating stars. He’s also anything but a one-woman man. “He’s very into threesomes,” she explains. “Even when he was with [a former girlfriend] , he was like, ‘I’ll pay you $20,000 a month,’ and he kind of even wanted us to be two girlfriends. I don’t think he would dare tell [Jennifer] about his threesomes; I truly believe he’s keeping a side of himself from her,” she says.

As far as J.Lo’s future prospects with Alex go, Lauren says that she hopes that they stay together and that Alex stops cheating, but she’s anything but optimistic, adding: “She would be an idiot to believe he’d be faithful.”